Humidity in crawl space that dryer vents into


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Old 09-18-14, 01:02 PM
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Humidity in crawl space that dryer vents into

Hi folks,

I have a crawlspace with a dirt floor mostly covered in plastic. I had to move some of it at one point in the spring because water was getting in during heavy rains in and was simply pooling on top of it. The water has been drained and the way cleared in case it happens again. The clothes dryer vents into the crawlspace. I did not open the vents on the side of the house this summer. There is a strong musty smell in the crawlspace. Any suggestions? Does it make sense to use the layered-plastic method if the dryer is venting in there and presumably adding humidity above it?

Marc
 
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Old 09-18-14, 01:06 PM
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You need to get the dryer vented outside the house - into a crawl space or an attic is a bad idea.

Then, once the water infiltration is addressed, get all of the dirt covered with plastic.

Finally, you have to decide: Crawlspaces either need to be sealed off from the house air and vented to the outside or sealed from the outside and tied to the conditioned air of the house.
 
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Old 09-18-14, 01:07 PM
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Dryer venting in crawl space adding to your problem. needs to vent outside
 
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Old 09-18-14, 01:15 PM
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Venting the dryer down there needs to change, way too much added moisture. The term "strong musty smell" is a polite way of saying you have mold down there and that can be more than a problem, a huge expense.

It sounds like you addressed some of the flood issue and that is good, but needs to be as good as possible. Then the plastic needs to be perfect and sealed up the walls. Not sure what you have for walls, but they need to be insulated and that space brought into the conditioned living space. Not that you are moving down there, unless someone gets in trouble , but the air in a basement or crawlspace filters up through the house and is a major part of the air you breathe.

Photo #5 in the link below is an ideal solution. The link has lots of information so I'll let you read.

Bud
BSI-009: New Light In Crawlspaces — Building Science Information
 
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Old 09-18-14, 01:28 PM
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Thanks everyone. I've looked into venting the dryer outside and the distance and angles required are not possible without serious reno. The walls are insulated and fireproofed and the ceiling of the crawlspace is insulated from the house.

I know it's not the ideal situation but if we assume that the dryer will always be venting down there what would be the best setup?
 
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Old 09-18-14, 01:34 PM
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Quit using the dryer.

After that, increase the exchange of air in the crawl space with the outside but that's not fixing anything - removing the insulation on the walls of the crawl space might help.
 
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Old 09-18-14, 02:24 PM
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How far is the dryer from an exterior wall? What is in the way of ducting the exhaust to the outside? Is there a floor above the dryer?
 
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Old 09-18-14, 02:40 PM
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Thanks to you both. Marksr, the problem is that it's a row house and to vent to the front would require a greater than 90 degree turn, which I don't think would be great for keeping things moving, and to vent to the back would require three 90 degree turns and about 25 ft of vent. I checked with the dryer manual a while ago and it just wasn't going to work. I suppose I could attach one of those boosters along the way but it starts to get a bit beyond my skills. I've contacted a local basement/crawlspace repair company for a quote on the whole shebang, hopefully they'll be skilled in both venting and encapsulating.

Almost forgot, yes, the dryer is on the first floor of a 2 storey building, if that's what you are asking.
 
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Old 09-18-14, 02:49 PM
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Not overly familiar since they don't exist around here but row house means you don't have space between you and your neighbor on each side, there's only air next to your house in the front and back, right? Another way, your side walls are your neighbors' side walls as well, right?

If so, then I can certainly see that front or back exhaust are the only options.

At the moment, your exhaust goes down from the first floor into the crawlspace. What if it went up into the ceiling? Are the joists aligned to do that or are they perpendicular to the run the vent would have? Front and back, what's between the laundry room and the outside walls?
 
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Old 09-18-14, 02:52 PM
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My dryer vent has one 90 degree turn and works fine but it's a short run - less than 8' How do the neighbors vent their dryers [assuming the houses are similar]? Sometimes it's best to vent thru the roof but not if it's got to go that high.
 
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Old 09-18-14, 02:57 PM
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Hi Mitch. Yes a row house means they're stuck together on both sides (as far as I use the term anyhow, I should probably look it up before using it again). I just took a look and it seems like it could vent up, over the kitchen, and out the back. The ceiling is a bit lower over the kitchen, sort of "boxed out", seemingly to hold an embedded light fixture and a ceiling fan, that would probably have room to run the vent through. Again, though, this is getting way beyond my skills (I'm a computer programmer!), although I do appreciate the insights as it makes me a more knowledgable client when dealing with home renovators.
 
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Old 09-18-14, 02:59 PM
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I'd look into what it might take to re-route the vent and I like Mark's idea about what the neighbors have in place. Know any of them well enough to invite yourself in to take a look?
 
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Old 09-18-14, 03:21 PM
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Marksr, I have a feeling the neighbours houses are more sane than mine. This was a duplex turned into a single-family dwelling sometime in the 80s and the layout is a bit strange. The roof is definitely too far.
 
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Old 10-06-14, 05:20 AM
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I've had a few contractors look at re-routing the dryer vent to the exterior back of the house (not legal in the front). One guy suggested that it go through the crawl space and out under the back porch. I asked if moisture would be a problem and he said no. The second contractor said that venting under the porch would cause moisture problems and that we would have to go up and through the ceiling of the main floor. Is it wise to run a lot of venting through a CS? I'm going to have it encapsulated and dehumidified once the dryer is rerouted. And is it possible to say definitively whether or not it's a bad idea to vent a dryer under a porch (it's quite low to the ground and extends ~6' from the house). The advantage of going through the CS is less cost and much less disruption and dust.

Thanks for any advice.
Marc
 
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Old 10-06-14, 05:50 AM
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Dryer

Move the dryer to the back porch.
 
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Old 10-06-14, 06:00 AM
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If the back porch has an open floor construction where all the rain drains below, then adding the dryer will change very little. Lint accumulation and lack of access to clean the dryer hood might be a concern. Also, if the exhaust will carry moisture up to the surface of the deck that could be an ice (slippery) issue.

Running through the crawlspace is fine, but in your cold climate best if encapsulated as stated.

With only 6' to go to exit from under the deck I would be considering ways to insulate and extend it the extra few feet. Check codes to be sure.

Bud
 
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Old 10-09-14, 11:36 AM
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Wirepuller, honestly, I've considered doing that.

Bud, it's a plywood-floored deck/porch, no drainage.
 
 

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